1. Field of the Invention
The present invention relates to a glass ceramic sintered body that is best suited as an insulating substrate in a wiring board used for packages for accommodating semiconductor devices (semiconductor packages), to a method of producing the glass ceramic sintered body and to a wiring board using the glass ceramic sintered body.
2. Description of the Related Art
In recent years of highly degree of information where information and communication technology is rapidly advancing, attempts have been made to further increase the speed and sizes of semiconductor devices. To meet these demands, it has also been desired that the wiring board used for the semiconductor packages have wiring layers of decreased resistance in the wiring board and a decreased dielectric constant to decrease transmission loss of signals. To fulfill the demand, there has been proposed a wiring board having an insulating substrate by using glass ceramics of a low dielectric constant, that can be densely formed upon firing at not higher than 1000° C. and that can be co-fired together with the wiring layer comprising a low-resistance metal such as copper, silver or gold as a chief component.
Here, semiconductor devices comprising chiefly silicon tend to exhibit decreasing mechanical strength as the devices are designed to operate at high speeds. When the semiconductor devices are mounted (primary mounting) on a package for accommodating semiconductor devices, therefore, a problem may arouse in that the semiconductor devices are destroyed due to thermal stress produced by mismatching in the thermal expansion-coefficient between the devices and the package. As the size of the device increases, further, the thermal stress increases correspondingly, and the devices become more probable to be damaged.
It has therefore been desired to decrease the thermal stress that affects the primary mounting by bringing the thermal expansion-coefficient of the package to meet the thermal expansion-coefficient (2 to 4×10−6/° C. at 40 to 400° C.) of silicon.
For example, Japanese Examined Patent Publication (Kokoku) No. 58198/1992 discloses a multi-layer ceramic circuit board having a small coefficient of thermal expansion by using, as an insulating material, a glass ceramic sintered body comprising mullite, quartz glass and borosilicate glass.
Further, Japanese Unexamined Patent Publication (Kokai) No. 254923/1993 discloses a ceramic insulating substrate having a small coefficient of thermal expansion capable of forming a wiring of low resistance by combining a borosilicate glass comprising SiO2, B2O3, K2O and Al2O3 with alumina, cordierite or quartz glass.
The wiring board using the above-mentioned conventional glass ceramic sintered body as an insulating substrate realizes a small coefficient of thermal expansion and makes it possible to improve reliability of the primary mounting. When mounted (secondary mounting) on a mother board constituted by a printed wiring board having a very large coefficient of thermal expansion (e.g., about 15 to 20×10−6/° C.), however, mismatching in the the thermal expansion-coefficient becomes very great to impair reliability in the secondary mounting.